• Nick R Miller, Alia L Yasen, Logan F Maynard, Li-Shan Chou, David R Howell, and Anita D Christie.
• Department of Human Physiology, University of Oregon , Eugene, OR , USA.
• Brain Inj. 2014 Jan 1; 28 (10): 1270-6.

Primary ObjectiveTo evaluate excitability and inhibition of the motor cortex acutely and longitudinally following mild traumatic brain injury (mTBI).Research DesignA longitudinal paired case-control design was used to examine cortical excitability and inhibition in 15 adults who had sustained an mTBI (mean age = 20.8 ± 1.2 years) and 15 matched control participants (mean age = 21.1 ± 1.3 years).Methods And ProceduresParticipants visited the lab within 72 hours of injury and again at 1, 2, 4 and 8 weeks post-injury. During each visit, transcranial magnetic stimulation was used to examine resting motor threshold (RMT), motor evoked potential peak-to-peak amplitude (MEPamp) and cortical silent period (CSP) duration of the first dorsal interosseous muscle.Main Outcomes And ResultsThere were no differences between groups in RMT (p = 0.10) or MEPamp (p = 0.22) at 72 hours post-injury or across the 2-month testing period (p ≥ 0.68), indicating similar cortical excitability. However, the CSP duration was higher in individuals with mTBI, indicating greater intra-cortical inhibition compared with the control group at 72 hours post-injury (p = 0.03) and throughout the 2 months of recovery (p = 0.009).ConclusionsmTBI appeared to have little effect on cortical excitability, but an acute and long-lasting effect on intra-cortical inhibition.

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